Line a baking sheet with parchment. Set a shallow bowl of confectioners' sugar nearby.
Warm cream, butter, lemon zest, and salt in a small saucepan until steaming, not boiling.
Remove from heat. Stir in lemon juice and lemon extract until combined.
Place chopped white chocolate in a heat-safe bowl. Pour hot cream mixture over it and let sit 2 minutes.
Stir slowly from the center until smooth and glossy. Microwave 5–10 seconds if a few bits remain.
Cover and chill until thick enough to scoop, about 60–90 minutes.
Scoop 1-tablespoon portions and roll quickly into balls. Place on the lined sheet.
Roll truffles in confectioners' sugar. For a shell, melt the optional white chocolate and dip, letting excess drip.
Chill 15 minutes to set. Keep refrigerated until serving.